Answer:
In my opinion I would way it is completely unacceptable for zoos, aquariums and research institutions to hold living creatures in captivity.
Explanation:
Animals should all be free and stop being oppressed and caged, as many animal cruelty movements fight for it. The only exception for zoos, aquariums and research institutions to exist is if they treat animals in need or try to develop solutions for them to live in better conditions.
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Just one comment
<em>(Take into account this paragraph expresses my own views and opinions, which may be different from yours)</em>
The answer should be Theme is not the moral of a story.
Im my opinoin id say both a and d but id go wit d to be safe